PROGRESS TOWARD MITIGATING URANYL PEROXIDE PRECIPITATION AND - PowerPoint PPT Presentation

S EPTEMBER 10-13, 2017 M ONTREAL M ARRIOTT C HATEAU C HAMPLAIN M ONTREAL , QC C ANADA PROGRESS TOWARD MITIGATING URANYL PEROXIDE PRECIPITATION AND CONTROLLING PU BEHAVIOR ON TITANIA AMANDA YOUKER Chemist Sergey Chemerisov, Michael Kalensky, Alex Brown, Kevin Quigley, Tom Brossard, James Byrnes, and George F. Vandegrift

LEU URANYL SULFATE SOLUTION FOR MO-99 PRODUCTION  Radiolysis of water produces hydrogen and hydrogen peroxide.  No large pH changes expected during irradiation in sulfate media  Hydrogen peroxide is an important radiolysis product. Buildup of peroxide can lead to precipitation of uranyl peroxide  Products of nitrate radiolysis do lead to peroxide destruction  Products of sulfate radiolysis do NOT affect peroxide destruction  Precipitation of uranyl peroxide occurred during irradiation of LEU uranyl sulfate solutions at our 3 MeV Van de Graaff accelerator 2

VAN DE GRAAFF EXPERIMENTS  0.5 and 2.0 mL uranyl sulfate (DU, NU, and LEU) samples irradiated  Gases measured in sweep gas via RGA  Samples temperature controlled  Various dose rates applied to samples 3

PRODUCTION AND DECOMPOSITION OF URANYL PEROXIDE UO 22+ + H 2 O 2 + n H 2 O ↔ ↓ UO 2 O 2 ·nH 2 O(s) + 2 H + Equation 1 UO 2 O 2 ·2H 2 O(s) + 2 H + → UO 22+ + H 2 O 2 Equation 2 H 2 O 2 → H 2 O + ½ O 2 Equation 3 UO 2 O 2 →UO 3 + ½ O 2 Equation 4 UO 3 + 2 H + → UO 22+ + H 2 O Equation 5  Radiolyis of water generates hydrogen peroxide and can react with uranyl ion to form uranyl peroxide  Two forms of uranyl peroxide can form studtite (n=4) and meta-studtite (n=2)  Two different mechanisms proposed by Silverman et. al. for uranyl peroxide decomposition (equation 2&3 and equation 4&5)  Temperature and addition of a catalyst play a role as well Silverman, M.D., Watson, G.M., and McDuffie, H.F. “Peroxide Decomposition in Aqueous Homogeneous Reactor Fuels.” Industrial and Engineering Chemistry , 8, 1238-1241 (1956). 4

DIFFERENT SOURCES OF URANIUM - Cr Fe Ni Cu Pt NO 3 Solution (ppm) (ppm) (ppm) (ppm) (ppm) (mM) NU - 140 g-U/L <0.25 <0.1 <0.05 0.41 0.54 0 DU - 185 g-U/L 9.6 81 6.3 4.2 0.02 500 LEU - 148 g-U/L 1.1 18 2.7 1.3 <0.01 0  VDG experiments used different sources of uranium  Various metal ions were present in solution  LEU used at VDG because it will be used for experiments at linac  Nitrate radiolysis products lead to destruction of hydrogen peroxide Bhattacharyya P.K., Saini R.D. Radiolytic yields G(HNO 2 ) and G(H 2 O 2 ) in the aqueous nitric acid system. – Int. J. Radiat. Phys. Chem. – 1973. – V. 5. – P. 91-99. 5

NU AND DU VDG RESULTS Apparent Average Estimated Measured Sample Dose Rate H 2 O 2 (µM) Precipitation Gas Generation H2 Measured Gas Generation O2 Overall H Steady Sample Type Current Total Dose H:O Ratio @ Temp (°C) (Mrad/min) ( μ moles/Mrad) ( μ moles/Mrad) to O Ratio State Time ( μ A) (Mrad) Steady State ( min) NU 62 19 13,600 44 130 NO 0.045 0.019 2.4 60 2.0 Delayed 1 NU - 30 μ M/L H2O2 added 64 20 15,800 47 390 0.079 0.036 2.2 45 2.2 NU - 17 μ M/L H2O2 added 80 20 16,000 48 60 NO 0.089 0.043 2.1 60 2.0 NU - 170 μ M/L H2O2 added 60 18 17,300 42 610 NO 0.065 0.031 2.1 83 2.1 NU - 4300 μ M/L H2O2 added 60 18 10,300 41 540 YES 0.075 0.049 1.5 140 2.1 NU - 2300 μ M/L H2O2 added 60 17 13,300 41 60 YES 0.122 0.087 1.4 140 2.0 Delayed 2 NU - 50 μ M/L H2O2 added 63 20 15,800 46 800 0.101 0.046 2.2 42 2.1 NU - 240 μ M/L H2O2 added 63 20 15,000 47 840 NO 0.104 0.047 2.2 50 2.1 NU - 130 μ M/L H2O2 added 60 18 15,000 41 880 NO 0.100 0.043 2.4 130 2.2 DU - 50 μ M/L H2O2 added 63 19 12,200 48 100 NO 0.011 0.005 2.2 25 2.2 DU - 55 μ M/L H2O2 added 63 20 14,900 46 6 NO 0.011 0.005 2.5 30 2.5 1 Sample was cloudy on 12/07/16, and precipitate was observed on 12/22/16. 2 Precipitate was observed on 12/06/16.  Hydrogen peroxide added prior to irradiation because precipitation did not occur in 2014- 2015  Delayed onset of precipitation where it occurred 8-21 days after irradiation  Apparent steady state (gas generation rates stabilize) and overall H 2 :O 2 ratios shown  DU solutions – lower gas production and no precipitation  Solubility limit of hydrogen peroxide is ~ 1 mM 6

GAS ANALYSIS RESULTS FOR NU SAMPLES  No precipitation  Delayed precipitation 7

DU RESULTS COMPARED TO NU RESULTS  DU sample  NU sample 8

LEU VDG RESULTS Average Estimated Apparent Measured H 2 O 2 Overall H to O Sample Dose Rate Measured Sample Type Current Total Dose Precipitation Steady State H:O Ratio @ Temp (°C) (Mrad/min) H 2 O 2 (µM) ( μ moles/Mrad) ( μ moles/Mrad) Ratio ( μ A) (Mrad) Time (min) Steady State 64 20 16,728 46 100 YES 0.135 0.054 2.5 60 2.3 LEU 62 19 13,990 43 17 YES 0.146 0.060 2.4 60 2.3 LEU LEU - Fe +2 @1000ppm 66 21 17,994 50 1300* NO 0.025 0.010 2.4 55 2.4 LEU - Fe +2 @1000ppm 32 5 4,150 12 2100* NO 0.011 0.002 5.4 252 3.1 LEU - Fe +2 @500ppm 66 22 18,519 51 16* NO 0.039 0.017 2.3 50 2.3 LEU - Fe +2 @500ppm 29 4 3,295 9 440* NO 0.057 0.023 2.5 107 2.3 LEU - Fe +2 @200ppm 30 4 3,575 10 2600* NO 0.048 0.019 2.5 173 2.4 LEU - Cu +2 @500ppm 34 5 4,541 12 1600* YES 0.066 0.027 2.5 N/A N/A LEU - Fe +2 & Cu +2 @100ppm 28 4 1,112 9 860* NO 0.032 0.011 2.7 N/A N/A LEU - Fe +3 @250ppm 30 4 1,336 11 1600* NO 0.030 0.009 3.2 N/A N/A * NaF was added as a complexant  Precipitation occurred in LEU solutions without additional catalysts added  200 ppm Fe 2+ ,250 ppm Fe 3+ , and 100 ppm Fe 2+ with 100 ppm Cu 2+ prevented precipitation  Total dose and dose rates applied to samples were varied  Temperatures were also varied 9

PEROXIDE DESTRUCTION BY FE 2+ Fe 2+ + H 2 O 2 → Fe 3+ + OH− + OH• Equation (7) OH• + H 2 O 2 → HO 2 • +H 2 O Equation (8) Fe 3+ + • 2HO → Fe 2+ + H + + O 2 Equation (9) Fe 2+ + • 2HO → Fe 3+ + HO 2 − Equation (10) Fe 2+ + OH• → F e3+ + OH − Equation (11) Total gas production decreases significantly when Fe 2+ is present  A possible explanation may be that Fe 3+ is acting as an electron scavenger (Fenton reaction, Fe 2+ is  oxidized to Fe 3+ by peroxide to form the OH radical (equation 7))  The radical goes on the decompose hydrogen peroxide. It also become the chain breaker by oxidizing Fe 2+ to Fe 3+ Fe 3+ can interact with solvated electron to form Fe 2+ , which is why Fe 2+ and Fe 3+ were both effective  at catalyzing peroxide destruction De Laat, J. and Gallard, H. “Catalytic Decomposition of Hydrogen Peroxide by Fe(III) in Homogeneous Aqueous Solution: Mechanism and Kinetic Modeling,” Environ. Sci. Technol . 33 , 2726-2732 (1999). 10

GAS ANALYSIS RESULTS FOR LEU SAMPLES  No catalyst – precipitation occurred  500 ppm Fe 2+ - precipitation did not occur 11

CONCLUSIONS FROM VDG PEROXIDE EXPERIMENTS  Precipitation of uranyl peroxide occurred in LEU samples without additional catalysts  Temperature and catalyst concentration play an important role in preventing uranyl peroxide precipitation  200 ppm Fe 2+ , 250 ppm Fe 3+ , and 100 ppm Fe 2+ with 100 ppm Cu 2+ all were successful at preventing precipitation  Delayed onset of uranyl-peroxide precipitation is concerning  Mini-AMORE experiments will follow – Fissioning and higher power densities in mini-AMORE  LEU samples will be irradiated with and without catalysts to look for uranyl peroxide precipitation 12

LEU URANYL SULFATE SOLUTION FOR MO-99 PRODUCTION  ~30 times more Pu-239 from LEU compared to HEU  Avoid generation of GTCC waste - >1 nCi/g Pu-239  Set of tracer experiments to investigate Pu behavior on titania in a sulfate media  Examined ways to control Pu behavior  Collected batch data  Tested batch data results in small-scale column setting Youker, A.J., Brown, M.A., Heltemes, T.A., and Vandegrift, G.F. Controlling Pu behavior on Titania: Implications for LEU Fission-Based Mo-99 Production. Ind. Eng. Chem. Research., 13 reviewer comments were addressed.

PU ADSORPTION ON TITANIA  Batch study results suggest better adsorption at higher temperature and lower acid concentration Youker, A.J., Brown, M.A., Heltemes, T.A., and Vandegrift, G.F. Controlling Pu behavior on Titania: Implications for LEU Fission-Based Mo-99 Production. Ind. Eng. Chem. Research., 14 reviewer comments were addressed.

COLUMN STUDY: TEMPERATURE EFFECTS Sample %Pu-239 80°C %Pu-239 25°C Column Effluent #1 8.7 20.4 Column Effluent #2 7.7 33.3 pH 1 H 2 SO 4 Wash 0.7 6.4 H 2 O Wash #1 0.1 0.4 1 M NaOH Strip 0.03 0.04 H 2 O Wash #2 0.0008 0.002 1 M H 2 SO 4 Wash 62.8 37.8 Sorbent contact with 1 4.5 2.6 M H 2 SO 4 Remaining Activity 15.2 0  0.66 cm X 1 cm L titania column  Direct down-scale column for plant-scale design  13.3 cm/min loading velocity and 6.7 cm/min stripping velocity Youker, A.J., Brown, M.A., Heltemes, T.A., and Vandegrift, G.F. Controlling Pu behavior on Titania: Implications for LEU Fission-Based Mo-99 Production. Ind. Eng. Chem. Research., 15 reviewer comments were addressed.